The overall objective is to characterize the molecular mechanisms involved in the tissue-specific control of the human apolipoprotein (apo) E/C-I/C- II gene locus. The genes in this locus are clustered in a 45-kb segment of chromosome 19, and their expression in various cell types appears to be determined by several distinct intergenic regulatory domains. For most cell types in which these genes are expressed, there are no tissue- specific control sequences in the promoters, making this gene locus somewhat unique in its overall regulatory scheme. To identify and partially characterize these tissue-specific control sequences, constructs that contain various portions of this locus will be used to generate transgenic mice, and the expression of the transgene will be determined by RNase protection analysis and in situ hybridization. After individual regulatory domains have been localized, their composition and organization will be defined further by examining the expression of constructs following their transfection into cultured cells. The functional roles of these control sequences in the regulation of each gene in the locus will be examined. In particular, these studies will focus on understanding the structural basis underlying the mechanisms of apoE gene expression in the liver, macrophage, and brain. Knowledge of the regulatory domains of this gene locus will be used to construct vectors for directing the expression of heterologous cDNAs in specific tissues in transgenic animals to generate models for the study of various diseases. These vectors will contain regulatory sequences and structures derived only from this locus to provide the best possible assurance of predictable transgene expression. Pursuit of these objectives should provide an understanding of the role of this gene locus, and the apoE gene in particular, in the development and pathology of atherosclerosis and neurological diseases such as AIzheimer's disease.